1. Field of the Art
This invention relates to a device which detects breakdown in AC voltage surge suppressors, and, more particularly, to a meltable, electrical conductor used in series with voltage surge suppressors that suppress voltage surges occurring in power lines of 120, 240 or 480 volts, for example, that operate at 50 Hz, 60 Hz, 400 Hz or some other frequency. That electrical conductor can also be employed to monitor surge current levels and waveforms.
2. Background of the Prior Art
It is well known that voltage surges occur across power lines. Unless these surges are suppressed, they can cause great damage to electrical equipment.
Known AC voltage surge suppressors will clamp voltage surges at a clamping voltage that is characteristic of the voltage surge suppressor. For example, metal oxide varistors can protect against very large voltage surges which occur in power lines.
However, voltage surge suppressors eventually break down, entering a short circuit condition, and are not able to clamp any further voltage surges. Therefore, it is also known to place a fuse in series with a voltage surge suppressor. When breakdown of the voltage surge suppressor occurs, the resulting short circuit condition causes the fuse to blow. This provides an indication that the voltage surge suppressor can no longer give voltage surge protection. This type of arrangement is disclosed in both Fussell, U.S. Pat. No. 4,023,071, and Dell Orfano, U.S. Pat. No. 4,089,032.
However, most fuses, when (used in this type of application, considerably shorten the life-span of the voltage surge suppressor. Therefore, although fuses provide an indication that the voltage surge suppressor is no longer capable of voltage surge suppression, most of them do this at the expense of the voltage surge suppressor's life-span.
Also, most fuses cannot withstand repeated surge voltages. Therefore, most fuses will not last very long and need to be frequently replaced even before breakdown of the voltage surge suppressor.
It has not been previously known which fuses shorten surge suppressor life-span or can withstand repeated surge voltages. Because of this, no device has been known which can effectively detect breakdown of voltage surge suppressors.